sched/balancing: Rename scheduler_tick() => sched_tick()

- Standardize on prefixing scheduler-internal functions defined
  in <linux/sched.h> with sched_*() prefix. scheduler_tick() was
  the only function using the scheduler_ prefix. Harmonize it.

- The other reason to rename it is the NOHZ scheduler tick
  handling functions are already named sched_tick_*().
  Make the 'git grep sched_tick' more meaningful.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Valentin Schneider <vschneid@redhat.com>
Reviewed-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Link: https://lore.kernel.org/r/20240308111819.1101550-3-mingo@kernel.org